Chair back height adjustment mechanism

ABSTRACT

An improved chair back mechanism for adjusting the height of a chair back which includes a pair of facing C-shaped brackets one of which is connected to the chair back and the other of which is connected to the chair back support. A partially threaded stud extends through aligned apertures in each of the horizontal legs of the C-shaped brackets and upon rotation of the stud one bracket will move vertically with respect to the other effecting an adjustment of the height of the chair back with respect to the chair back support and the remainder of the chair.

ruted States Patent 11 1 1 1 3,917 Albinson 1 Nov. 4, 1975 CHAIR BACK HEIGHT ADJUSTMENT 2,708,474 5/1955 Lindroth 297/343 MECHANISM 3,059,736 10/1962 Boyd 3,086,222 4/1963 Hall et al. 297/353 X Inventor: Don Albmson, Coopersburg, 3,526,430 9/1970 Eldon 297/353 [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh Pa Przmary Examiner-Roy D. Frazier Assistant Examiner-William E. Lyddane Flledi y 28, 1974 Attorney, Agent, or Firm-B. R1 Studebaker [21] Appl. No.: 473,951

[57] ABSTRACT An improved chair back mechanism for adjusting the 81.2 height of a chair back which includes a p of facing [58] Fieid S 348 353 C-shaped brackets one of which is connected to the 297/42l 248/161 5 4 chair back and the other of which is connected to the chair back support. A partially threaded stud extends through aligned apertures in each of the horizontal [56] References Cited legs of the C-shaped brackets and upon rotation of the UNITED STATES PATENTS stud one bracket will move vertically with respect to 320,844 6/1885 Burk 297/353 UX the other effecting an adjustment of the height of the 781,090 1/1905 Perkins chair back with respect' to the chair back support and 2,281,038 4/1942 Jones the remainder of the chain 2,608,239 8/1952 Gorden... 1 2,702,214 2/1955 Turner 403/7 1 Claim, 4 Drawing Figures US. Patent Nov. 4, 1975 Sheet 1 of2 3,917,341

g; No

Will H NOE US. Patent Nov. 4, 1975 Sheet 2 of 2 3,917,341

1 CHAIR BACK I-IEIGHT ADJUSTMENT MECHANISM BACKGROUND OF THE INVENTION One must only encounter a large gathering of people to become readily aware of the fact that the size and shape of the individuals who make up our population differ widely. It will also be apparent to one who is knowledgeable with respect to the modern business of fice that many people spend the majority of their working day in their office chair. Although it is clearly impossible in the mass production of office furniture to manufacture chairs to the human specifications of each individual who will use a chair it is desirable that a mass produced chair be adjustable in several different ways to not only fit the user but to make the office worker as comfortable as possible. One important chair adjustment is the height of the chair back and this invention relates to a novel mechanism for adjusting the height of the chair back with respect to the remainder of the chair.

Although the height of a chair back is usually only adjusted at the time of acquisition by the user and will remain that way until a different person acquires the chair for extended use before it is adjusted again, the adjustability of the chair back still must be provided. A chair back adjustment mechanism, by virtue of the very nature of its mechanical parts, detracts from the aesthetics of the chair and it is preferable that a chair back adjustment mechanism be hidden within the chair body. Additionally, when the adjustment hardware extends from the back of the chair it can significantly scratch and mar adjacent office furnishings unless the chair user is extremely careful. Several prior art chair back adjustment mechanisms have been employed to adjust the height of the chair back and include the bolt and slot with latch lever mechanism disclosed in US. Pat. No. 2,168,620 which is visible at the back of the chair but does provide for a infinite number of positions between the highest and lowest adjustment, complex ratchet and latch mechanisms of the type disclosed in U.S. Pat. No. 2,509,102 and slot and projection mechanisms which provide only a fixed number of positions but which may be hidden within the back of the chair for aesthetic purposes as disclosed in U.S. Pat. No. 3,526,430. The majority of these prior art back height adjustment mechanisms either suffer from complexity, are required to be visually exposed for access or do not provide for an infinite number of intermediate height positions between the highest and lowest positions for the chair back.

SUMMARY OF THE INVENTION The chair back height adjustment mechanism of this invention obviates the composite prior art defficiencies by providing a simple mechanical adjustment mechanism which can be completely enclosed within the back of the chair, provides for an infinite number of positions between the highest and lowest height adjustments and employs a simple positive mechanical action not subject to failure through repetitive usage. The foregoing is accomplished in accordance with the present invention by providing in a chair including a base portion, a seat portion, a pair of back mounting arms extending from the base portion and a chair back including a structural chair back member enclosed within the chair back, the improved chair back height adjustment mechanism of this invention. This chair back height adjustment mechanism includes a back support member extending between the back mounting arms, a first Cshaped bracket secured to the back support member and having a pair of vertically aligned apertures in each of its horizontally extending arms, a second C-shaped bracket secured to the structural chair back member and facing in an opposed relationship to the first C-shaped bracket which also includes a pair of vertically aligned apertures in each of its horizontally extending arms, and an at least partially threaded stud which extends through the vertically aligned apertures in both of the C-shaped brackets. At least one of the apertures in one of the brackets includes threadswhich are constructed and arranged to coact with the threads on the stud to provide relative linear movement between the one C-shaped bracket and stud in response to rotation of the stud with at least one of the apertures in the other C-shaped, bracket being secured to the stud for linear movement therewith while permitting rotation of the stud with respect thereto. The chair back shell completely encloses the structural chair back member and the back support member is connected to the back mounting arms through openings in the sides of the chair back shell while an aperture in one of the top and bottom edges of the chair back shell provides access to tool receiving means on the stud. I

BRIEF DESCRIPTION OF THE DRAWINGS Many of the attendant advantages of the present in vention will become more readily apparent and better understood as the following detailed description is considered in connection with the accompanying drawings in which:

FIG. I is a side elevational view of a typical chair which may employ the chair back height adjustment mechanism of this invention;

FIG. 2 is a side elevation view partly in section illustrating the back heightadjustment mechanism of this invention;

FIG. 3 is an isometric view of the back height adjustment mechanism connected to the back support bar; and

FIG. 4 is a full size side elevation view of the back height adjustment mechanism of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawings wherein like reference characters represent like parts throughout the several views there is illustrated in FIG. 1 a chair representative of typical office seating generally designated 10. The chair [0 includes a base 12 typically supported on a plurality of casters 14 and having a threaded shaft 16 connected to a tilt mechanism (not shown) hidden within the seat 18. An adjusting collar 20 is typically employed between the base 12 and the seat 18 to adjust the height of the seat with respect to the floor. The seat of a standard office chair will generally include a structural support member (not shown) hidden within a molded plastic bottom cover 22 and carrying a cushion and cushion cover 24. In a typical chair, arms are provided at 26 which are conventionally fixed to the structural seat member with the chair back being typically supported by a vertical member extending from the chair tilt mechanism proximate the middle of the back of the seat upwardly to support the back. In the chair illustrated in FIG. I the structural relationship of the tilt mechanism arms and back are constructed in accordance with the teachings of application Ser. No.473,965 for Improved Chair Structure and Tilt Mechanism Therefor, filed the same day as this application by the same inventor and owned by the same assignee as this application. In this regard, the arms 26 are connected directly at 28 to laterally projecting arms extending from the tilt mechanism and the back is supported directly from the arms at 30 through the chair back support member 32 which extends across the back of the chair and is connected to small arm projections by being bolted thereto or similarly at 34 providing a unique construction wherein the arms tilt in conjunction with the chair back in a manner described in detail in said copending application as opposed to the typical office chair construction wherein the back alone tilts with respect to the arms which are either stationary or move only in conjunction with a seat tilt oflesser degree.

The chair back height adjustment mechanism of this invention is supported midway along the back support member 32. In this regard, a first C-shaped member or bracket 36 is bolted, welded or riveted as at 38 to the back support member 32. The C-shaped member 36 has in its horizontally extending arms 40 a pair of aligned apertures 42 one of which has a raised internally threaded portion 44. A second C-shaped member or bracket 46 having a pair of horizontally extending arms 48 with apertures 50 therethrough is arranged so that the apertures 50 and the apertures 42 are aligned. A partially threaded stud 52 having a threaded portion 54 and a reduced diameter portion 56 extends through the apertures 42 and 50. The second C-shaped member 46 is fixed by bolts, welding or rivets at 58 to the rigid chair back structural member 60. The reduced diameter portion 56 of the partially threaded stud 52 extends through the upper aperture 50 of the C-shaped member 46 and an E clip retaining ring 62 or similar radius expanding device is employed to retain the upper horizontal arm 48 of the C-shaped member 46 fixed with respect to the stud 52 at the upper end thereof.

The bottom end of the partially threaded stud 52 includes tool receiving means 64-which may be in the form of a hexagonal end or a screwdriver slot or any similar configuration that can provide for rotation of bottom end of the stud and hence the tool receiving means 64. Lateral openings 72 are also provided in the side walls of the molded plastic chair back shell 68 through which the arms 26 are connected to the back support member 32 as indicated at 30 in FIG. 1.

In operation, the first C-shaped member 36 is fixed to the back support member 32 and receives in its upperthreaded aperture 42 the threaded stud S2. The other C-shaped member 46 is secured through its upper horizontal arm 48 to the threaded stud 52 for vertical movement therewith while permitting rotation of the stud with respect thereto. Through the fixed mounting at 58 of the C-shaped member 46m the rigid chair back structural member 60, the stud, C-shaped member 46 and chair back structural member will move in unison and be caused to move vertically either upwardly or downwardly in response to coaction between the threads 54 and the threaded apertures 42, 44 when the stud is rotated.

It will be apparent that when a tool is inserted through the aperture 70 in the molded chair back 68 it acts upon the tool receiving means 64 to rotate the stud 52. Rotation of the stud 52 will cause the chair back to be adjusted either upwardly or downwardly depending on the direction of rotation of the stud 52 to any posi-. tion defined by the length of the'threaded portion 54 of the stud 52. Preferably, this distance for a typical office chair would provide for an adjustment of about 2% inches and such adjustment range should be satisfactory to accommodate any of the various chair users.

It will also be apparent that within the concept of this invention the entire back height adjustment mechanism may be inverted with access to the tool receiving means As will be apparent from the foregoing the chair back height adjustment mechanism of this invention is completely hidden within the confines of the chair back, provides aninfinite number of positions between the confines of its upper and lower limits and is mechania cally simple and easily accessible while not detracting from the aesthetics of the chair itself.

What is claimed is: l. A chair comprising, in combination:. a base portion, a seat portion mounted on said base portion,

a pair of back mounting arms extending from said base portion on either side of said seat portion,

a chair back including a structural chair back member completely enclosed within said chairback,

a back support member extending through openings in the sides of said chair .back and connected between said back mounting arms,

a first C-shaped bracket secured to said back support member having a pair of vertically aligned apertures, one in each of the horizontally extending arms thereof,

a second C-shaped bracket secured to the structural chair back member and facing in an opposed relationship to said first C-shaped bracket, said second C-shaped bracket also including a pair of vertically aligned apertures, one in each of the horizontally extending arms thereof, and

an at least partially threaded stud including at one end thereof tool receiving means whereby rotation may be imparted to said stud, said stud extending through each of said vertically aligned apertures in both said first and said second C-shaped brackets,

at least one of said apertures in one of said C- shaped brackets including threads therein constructed and arranged to coact with the threads on i said stud to provide a relative linear movement be- I tween said one C-shaped bracket and said stud in shaped brackets and said partially threaded stud response to rotation of said stud, at least one of said being completely enclosed within said chair back apertures in the other of said C-shaped brackets and said chair back including an aperture in the being loosely secured to said stud for linear movebottom edge thereof to provide access to said tool ment therewith while permitting rotation of said 5 receiving means on said stud. stud with respect thereto, said first and second C- 

1. A chair comprising, in combination: a base portion, a seat portion mounted on said base portion, a pair of back mounting arms extending from said base portion on either side of said seat portion, a chair back including a structural chair back member completely enclosed within said chair back, a back support member extending through openings in the sides of said chair back and connected between said back mounting arms, a first C-shaped bracket secured to said back support member having a pair of vertically aligned apertures, one in each of the horizontally extending arms thereof, a second C-shaped bracket secured to the structural chair back member and facing in an opposed relationship to said first Cshaped bracket, said second C-shaped bracket also including a pair of vertically aligned apertures, one in each of the horizontally extending arms thereof, and an at least partially threaded stud including at one end thereof tool receiving means whereby rotation may be imparted to said stud, said stud extending through each of said vertically aligned apertures in both said first and said second C-shaped brackets, at least one of said apertures in one of said Cshaped brackets including threads therein constructed and arranged to coact with the threads on said stud to provide a relative linear movement between said one C-shaped bracket and said stud in response to rotation of said stud, at least one of said apertures in the other of said C-shaped brackets being loosely secured to said stud for linear movement therewith while permitting rotation of said stud with respect thereto, said first and second C-shaped brackets and said partially threaded stud being completely enclosed within said chair back and said chair back including an aperture in the bottom edge thereof to provide access to said tool receiving means on said stud. 